Process for protecting galvanized iron against attack by strong acids



CROSS REFEREiiCE tiililllllllttt United States Patent Germany, acorporation of Germany No Drawing. Filed July 23, 1964, Ser. No. 384,779Claims priority, applicfitigg sGzesr-many, Sept. 14, 1963,

9 Claims. (Cl: 2sz-79.4

The present invention relates to a process of protecting galvanized ironagainst attack by strong acid and more 3,328,303 Patented June 27, 1967ice Example I A galvanized steel wire (40 mm. in length, diameter of 3.5mm.) having a zinc coating of l6-l7 was inserted into 1.33 Nhydrochloric acid. The time required for 10% of the zinc coating to bedissolved was determined and in a similar manner the dissolution timeswith various inhibitor additives present was determined. The results areshown in the following table:

TABLE Dissolution of 10% of the 1.33 N hydrochloric acid: zinc coating(seconds;

particularly the invention relates to a process of protect- Without anyadditive ing galvanized iron against attack by strong acid by in- 0.2%quinoidine 110 corporating in the acid treatment agent in addition to0.1% acrldine 110 uinoidine a small amount of a guinoline deri'va'tiv"'e,. 0.2% qumoidme+0.1% acndme 840 It is known that quinoidine, whichis obtained as a by- Example 2 product in the manufacture of quinineacts to curb the attack of strong acids upon various metals (DRP 548315). The above-named compound has achieved considerable importance as acorrosion-inhibitor during the past few years and is marketed under thename Brindi. However, it has been observed that the protective effect ofthe Dissolution of 10% of the quinoidine is greatly diminished in thoseinstances in 2 Nhydrochloric acid: zinc coating (seconds) which iron andzinc are simultaneously present so that Without additive 10 they areboth subject to the attack by the acid at the 0.3% quinodine 60 sametime as for instance happens when the two metals 0.2% 2-phenylquinoline210 are conductively interconnected. In such instances, as for 0.3%quinoidine+0.2% 2 phenylquinoline 680 example, in the case of galvanizediron, the zinc as an E I 3 anode is preferentially attacked by the acidgiving rise xamp e to the formation of corrosion elements. As a result,the galvanization of the iron (zinc coating) is dissolved within arelatively short period of time, whereupon the iron very rapidlyundergoes corrosion and disintegration.

It is, therefore, an object of the present invention to provide a simpleprocess of protecting galvanized iron against an attack by a strong acidutilizing quinoidine and a quinoline derivative as protective agentwhereby the above-enumerated disadvantages and deficiencies of Agalvanized steel wire mm. long, 3 mm. diameter, 8.5 1. zinc coating) theends of which had been coated with a layer of parafiin in order toeliminate as much as possible the formation of local elements(corrosion) along the ends of the wire was employed. The wire wasinserted into 2 N hydrochloric acid and the time taken for 5% of thezinc coating to be dissolved determined in the absence of any additiveas well as the additives as hereinafter set out.

the final products are overcome. 40 Dissolution of 5% of the It is afurther object of the present invention to pro- 2 N hydrochloric acid:zinc coating (seconds) vide a process for protecting galvanized ironagainst at- Without additive 12 tack by strong acids which process hasthe advantage that 0.3% quinoidine 65 the result achieved by the use ofthe additional additive 0.1% 7,8-benzoquinoline 420 is considerablygreater than could have been anticipated 0.3% quinoidine+0.l%7,8-benzoquinoline 1140 from the results achieved from either alone.

Other objects and advantages of the present invention will be apparentfrom the further reading of the specification and the appended claims.

In accordance with the invention it has now been found that theprotection from acid of galvanized iron provided by incorporatingquinoidine into the acid agents which come into contact with the same isconsiderably improved if there is additionally included in such agents asmall Example 4 amount of a quinoline derivative. In accordance with the0.3% q inoidine 30 invention it is preferable to use such quinolines asare 0.3% 9-phenylacridine 8 condensed with and/or substituted by abenzene ring, as 03% q n0 i -p y n 570 for example, acridine,phenanthridin, 7-8-benzoquinoline,

Example 5 Z-phenylqurnohne, or 9-phenylacr1d1ne.-

It is known that the speed of dissolution of metals may A galvamzedstecl wll'e long, 3 dlametel') be inhibited by various simple quinolinederivatives, such as acridine (Zeitschrift fuer anorganische Chemie,233/ 1937, page 236 et seq.). However, it has been established that theprotective effect of these inhibitors is insufficient against the attackof acid upon galvanized iron. As illustrated by the following examples,if a combination of the aforementioned quinoline derivatives andquinoidine is used, the protective effect is markedly enhanced and isgreater than could be expected from the efiect of the having a zinccoating of 10; was inserted into 2 N hydrochloric acid. The time fordissolution of 5% of the zinc coating was determined and in a similarmanner there were determined the corresponding periods required wheninhibitor-additives were present. The results are shown in the followingtable:

Dissolution of 5% of the 2 N hydrochloric acid: zinc coating (seconds)Without additive 6 individual components and is in fact a synergisticeffect. 0.3% quinoidine 3.--..- 51 The following examples are given byway of illustration 0.2% phenanthridine 72 and not limitation: 0.3%quinoidine-H12 phenanthridine 192 Similar results as in the above shownexamples, demonstrating the synergistic etfect of quinoidine and aquinoline derivative are obtained by using sulfuric acid instead ofhydrochlorc acid.

The amount of quinoline derivatives can be varied from 0.05 to 2%, thepreferred amount being from 0.1 to 0.5%. The amount of quinoidine canalso be varied from 0.05 to 2%, the preferred amount being from 0.1 to0.5%. The lower limits of amounts are given by the efiectiveness ofprotection, the upper limits are given by the price of the products.

It is within the scope of this invention that further additives can begiven to the acid solution such as surfactants and dyes. Preferredsurfactants are those which are resistant to strong acids, such asalkylphenolpolyglycolether (for instance HOSTAPAL or ARKOPAL fromFarbwerke Hoechst and LENSODEL from the Shell Corp.). If desired, alsoindicator dyes can be added; i.e. pH-indicators for proving theeffectiveness of the products.

What is claimed is:

1. In the process for protecting galvanized iron from attack of strongacids by incorporating 0.05 to 2% of quinoidine in said acid prior tothe application thereof to the galvanized iron, the improvement ofadditionally incorporatng in said acid 0.05-2% of a member selected fromthe group consisting of acridine, phenanthridine, 7,8- benzoquinoline,Z-phenylquinoline and 9-phenylacridine.

2. Improvement according to claim 1 which comprises incorporating0.1-0.5% of said group member into said acid.

3. Improvement according to claim 1 wherein said strong acid is a memberselected from the group consisting of hydrochloric and sulfuric acid.

I 4. A composition for protecting galvanized iron against attack fromstrong acid comprising a mixture of (A) quinoidine and (B) a memberselected from the group consisting of acridine, phenanthridine,7,8-benzoquinoline, 2-phenyl-quino1ine and 9-phenylacridine in a ratioof A:B of 1-40240-1.

5. A composition for protecting galvanized iron against attack fromstrong acid comprising a mixture of quinoidine and acridine in a ratioof 2:1.

6. A composition for protecting galvanized iron against attack fromstrong acid comprising a mixture of quinoidine and Z-phenylquinoline ina ratio of 3:2.

7. A composition for protecting galvanized iron against attack fromstrong acid comprising a mixture of quinoidine and 7,8-benz0quinoline ina ratio of 3:1.

8. A composition for protecting galvanized iron against attack fromstrong acid comprising a mixture of quinoidine and 9-phenylacridine in aratio of 1:1.

9. A composition for protecting galvanized iron against attack fromstrong acid comprising a mixture of quinoidine and phenanthn'dine in aratio of 3:2.

References Cited UNITED STATES PATENTS 1,746,677 2/ 1930 Rhodes 252-1482,167,621 8/1939 Beaver 252-148 2,499,283 2/ 1950 Robinson 252-1482,694,001 11/1954 Hayes et a1. 252-794 2,965,577 12/ 1960 Heimann et a1252-148 3,135,632 6/1964 Lucas et a1 252-794 XR ALEXANDER H. BRODMERKEL,Primary Examiner.

L, B. HAYES, Assistant Examiner.

1. IN THE PROCESS FOR PROTECTING GALVANIZED IRON FROM ATTACK OF STRONGACIDS BY INCORPORATING 0.05 TO 2% OF QUINOIDINE IN SAID ACID PRIOR TOTHE APPLICATION THEREOF TO THE GALVANIZED IRON, THE IMPROVEMENT OFADDITIONALLY INCORPORATING IN SAID ACID 0.05-2% OF A MEMBER SELECTEDFROM THE GROUP CONSISTING OF ACRIDINE, PHENANTHRIDINE,7,8BENZOQUINOLINE, 2-PHENYLQUINOLINE AND 9-PHENYLARIDINE.